1. Field of the Invention
The present invention relates to architecture of a serial communication circuit used in In-Flight Entertainment Systems on aircraft. In particular, the present invention relates to the use of a single Universal Asynchronous Receiver and Transmitter (UART) in a multipoint communication to reduce hardware utilization.
2. Description of Related Art
In-Flight Entertainment Systems (IFES) are now becoming popular on commercial aircraft. A typical new IFES may offer a variety of services including music, news, movies, video on demand, telephone, and games to passengers right at the passengers' seats with the convenience of individualized control. A timetable is generally provided from which a passenger may choose options when he or she requests services. Such a system involves a large number of interconnections to various peripheral subsystems. The communication between these subsystems and the main processor (or the host processor) can be quite complex. A host processor, referred to as a System Control Unit (SCU), communicates with a large number of external Line Replacement Units (LRUs) for various operational and control functions, such as overhead display, video and audio control. To facilitate the communication between the display units and the control units, multipoint serial communication is employed. The serial communication among these units typically requires a large number of Universal Asynchronous Receiver and Transmitters (UARTs).
The serial communication in an IFES environment may consist of a number of UARTs at the SCU communicating with a number of UARTs at the LRUs through a number of transceivers. In one known system, multiple transceivers of the UARTs at the LRUs are tied together to form a single communication link to one transceiver of the UART at the control unit. The problem with this system is that it does not support isolatable topology of serial communication. Isolated serial links for command are important for a number of reasons. The first reason is increased fault tolerance: a failure of one transceiver in one communication link does not have any effect on the remaining links. The second reason is that the SCU can send individual control information, if desired, to each of the UARTs instead of broadcasting to all of them. The third reason is that isolatable topology provides flexibility in routing the connections.
Another way to provide isolatable serial communication links employs N UARTs at the control unit, one for each of the N UARTs at the display units. This method, however, requires a large number of UARTs and transceivers at the SCU. In a typical IFES environment, this number could be prohibitively high. In addition, since each UART has its own input/output (I/O) address, the I/O address space to accommodate these devices may not be sufficient, especially when embedded control microprocessors or microcontrollers with limited I/O address space are employed.
It is therefore desirable to have a serial communication system in an IFES environment which provides isolatable serial communication link between the System Control Unit and the display units at the passenger's seats, and at the same time occupies as few I/O addresses as possible.